In recent years, centrally controlled network architectures have been proposed. As an example of a centrally controlled network architecture, there is a technology called OpenFlow (refer to Patent Literature (PTL) 1 and Non Patent Literatures (NPL) 1 and 2).
OpenFlow treats communication as an end-to-end flow, and performs path control, failure recovery, load balancing, and optimization for each flow. An OpenFlow switch specified in Non Patent Literature 2 comprises a secure channel for communicating with an OpenFlow controller that corresponds to a control apparatus, and operates according to a flow table given an appropriate instruction of addition or rewrite by an OpenFlow controller. In the flow table, a set of a packet matching rule (header fields) that matches a packet header, flow statistics (Counters), and an action (Actions) that defines a processing content is defined for each flow (refer to FIG. 11).
Upon receiving a packet, the OpenFlow switch searches an entry having a matching rule (refer to the header fields in FIG. 11) that matches the header information of the received packet in the flow table. When an entry matching the received packet is found as a result, the OpenFlow switch updates the flow statistics (Counter) and performs the processing content (packet transmission from a designated port, flooding, discard, etc.) written in the action field of the entry on the received packet. Meanwhile, when no entry matching the received packet is found as a result of the search, the OpenFlow switch forwards the received packet to the OpenFlow controller via the secure channel, requesting the controller to determine the path of the packet based on the source/destination of the received packet, receives a flow entry realizing this, and updates the flow table. As described, the OpenFlow switch forwards packets using entries stored in the flow table as processing rules.    PTL 1:    WO Publication No. WO2008/095010    NPL 1:    McKeown, Nick, et al., “OpenFlow: Enabling Innovation in Campus Networks,” [online], [searched on Aug. 16, 2011], the Internet <URL:    http://www.openflowswitch.org/documents/openflow-wp-latest. pdf>    NPL 2:    “OpenFlow Switch Specification” Version 1.1.0 Implemented (Wire Protocol 0x02), [online], [searched on Aug. 16, 2011], the Internet <URL:    http://www.openflowswitch.org/documents/openflow-spec-v1.1.0.pdf>